Process for the production of pigments.



Nm 847,032. "PATENTED MAR. 1'2, 1907.v

^ c. P. TowNsEND.

PROCESS FOR ,THE PRODUCTION- of PIGMENTS.

APPLICATION FILED APR.1'B:, 1902. BENEWED FEB. 11, 1907.

IIS

UNITED STATES PATENT oEEICE. CLINTON P. TCWNSENI), CEWASIIINCTCN, DISTRICT or COLUMBIA, ASSIGNOE TC'ELMER A. SPERRY, oF CLEVELAND, CHIC.- I

PROCESS son THE PnoDuoTroNoF Plc-:. MEN-rs'.

:at-enten Maren 12, i907.

App'umon fue@ Amir 1a, 1902. Renswearetruary 11, 1907 sentirlo. @5mnI To (LM w'ltom/.lt ntrtf/ (zu/werft:

Be it known that I,.CLINTN P. TowNsEND, 'a citizen of the United States, residing at y Washington, District of Columbia, haveinvented Certain new and useful Improvements in Processes for the Production of Pigmente, of which the following is a specification. y

This invention relates tothe reduction of pigments, and particularly to t eproduction of hydrated carbonate of lead or white lead,

and consists of a process forthe production of such pigments. It has been proposed heretofore to form such pigments electrolytically; but theA product has been found to be irregular in composition and quality and deficient incovering oWer.

I have' discovere that a pi ment of uniform grade and exceptionally iigh covering ower may be produced in an electrolytic cell and that the "condition essential thereto is a definite circulation of the electrolyte successively past the respective electrodes, and preferably in the direction from the anode pastor through the cathode.

, In the accompanying drawings I have shown several types of cell suitable for carrying out myjmethod. .It Will be understood f that any type or form of cell may be employed. v

.Fi ure 1 shows in cross-section a cell provide 4with perforated cathodes Fig. 2,' a cell in which both anodegmd cathode are of plate form, and Fig. 3 a form of cellemploying pervious anodes and cathodes.

' Referring to Fig. 1., the cell A is represented'as built up of a-series of sections a b c d,secured together by bolts e,' The sections a band c d clamp between them the plates C, which may be formed of perforated metal or'of wire-gauze and which constitute the cathodes of the apparatus. lhe sections are'so formed as to provide between theml and between them'and the sides of the cell a The lateralchannels g g .,gthe central channel efora purpose hereafter stated." H represents a filter-press of any preferred type communicatingwith the outlet- 5;

pipes D through pipe G and connections F. For this filter-press a settling-tank or other separatipg device may be substituted. The filtered electrolyte passes from the press H into the tank I and is thence returned to-the 6o 'cell through pipe J and easing K. As al -means for effecting the circulation of the electrolyte I have illustrated a propeller M,

'mounted upon a shaft L and driven by a The shaft L is preferably hollow,

pulley N. and through it carbon dioxid may be introduced' into the cell, thereby assisting in the circulation of th e electrolyte and regenerating the s ame.

z, represents the pipe for introducing water 7o into theelectrolyte Such water is preferably introduced, as shown, through the iilterpress and employed for Washing the pigment. lIhe valves E are provided in the pipes l), and

by opening them to a greater or less extent a rapid and repeated circulation may be secured through the cell, a portion only of the circulating electrolyte being continuously drawn f ioff. through the filter-press.

In the construction shown in Fig. 2 the cell 8e A is providedwith a bottom section a" in the form of an inverted wedge in order that no pigment may cblleet in the lower portion of the cell. rlhe electrodesB C are plates placed, respectively, in the neighborhood of the inlet and outlet of thecell. In the construction shown in Fig. 3 a tank A2 is provided With a false bottom 'I`,4which serves to support the divided. anode .13. The cathode C2 is in the form of a perforated plate trans-.9o

versely of the tank at its upper portion. The

electrolyte overflowing through the cathode is collected in the trough O andconducted through the pipe P to the seliaratinff devices.

The clear electrolyte is returned to tIie cell by '9 5 introduced i oo IOy alytic reduction itself proceeds more slowly as consisting of lead in divided form and may be in the form of bars or fragments of lead or of lead sponge or -lead in any intermediate form of subdivision.

It will be seen that in Fig. 1 the circulation of the electrolyte proceeds from the anode through the cathodes and thence toa point exterior to the field of electrolysis, at which point a separation of the pigment is effected. In Fig. 2 the circulation proceeds from the anode past the cathode and thence from the cell. In Fig. 3 the circulation is through the anode and. cathode successively. In certain cases it may be found desirable to reverse the direction of this circulation.

It will be understood that in the cases illustrated not only does the electrolyte circulate from the anode past or through the cathode, but that the pigment or insoluble compound formed at the anode detaches itself therefrom and is carried upwardly by the electrolyte past or through the cathode and thence to a region outside the field of electrolysis. It will be further seen that in the constructions shown in Figs. 1 and 3 the area of the cathode is greatly reduced as compared with that of the anode. This is of great assistance in preventing the formation of lead sponge by reduction of the pigment, not only because the speed of circulation through the cathode is thereby increased and the pigment prevented from adhering to it, but because the electro- When the cathode area is relatively small and the current density at the cathode relatively high.

In operation a lead lanode is employed and an electrolytev consisting of any salt whose acid radical forms a soluble compound with lead. To this solution is added a soluble carbonate. In practice I have 4found a mixture of sodium nitrate or acetate and sodium carbonato, in` proportions approximating ten to one, to constitute a satisfactory electrolyte. The current density depends to some extent on the speed of circulation of the electrolyte, a higher current density being einployed as this circulation is more rapid. 5

'lo regenerate the electrolyte, it is necesl sary to add thereto continuously or at interl vals carbon dioxid and water in quantity equal to that removed by the pigment. The l carbon dioxid may be emplol ed, as shown, to

aid or as the sole agent for e ectingthe circulation of the electrolyte.

I claiml l. The method of roducing White lead which consists in passing an electric current from a lead anode to a cathode through an electrolyte capable of yielding a lead solventl and containing a carbonating agent, causing the electrolyte to flow past an electrode and thence to a point outside the field of electrolysis atsuiiicient velocity to transport the pigment, and transportingthe pigment by such flow, substantially as described.

2. The method of roducing white lead which consists in passing an electric current from a lead anode to a cathode through an electrolyte capable of yielding a lead solvent and containing a carbonating agent, causing the electrolyte to flow past the anode and thence to apoint outside the field of electrolysis at sufficient velocity to transport the pigment, and transporting the pigment by such flow, substantially as described.

3. The method of producing white lead which consists in passing an electric current from a lead anode to a cathode through an electrolyte capable of yielding a lead solvent and containing a carbonating a 4ent, causing the electrolyte to flow between t e electrodes and thence to a point outside the field of electrol ysis at sufficient velocity to transport the pigment, and transporting the such flow, substantially as descri ed. l

4. The method of producing white' lead which consists in passing an electric current from a lead anode to a cathode through an electrolyte capable of yielding a leadv solvent and containing a carbonating agent, causing the electrolyte to How repeatedly past an electrode and thence to a point outside the Ifield of electrolysis at sufficient velocity to transport the pigment, and transporting the pigment by such iiow,k substantially as, described.

vIn testimony whereof IA affix my signature in presence of two witnesses.

CLINTON P. TOWNSEND.

Witnesses Pintor B. HILLS, EUGENE A. BYRNES.

pigment by i 

